Practical Standalone Tuning: Step 3: Base Table Configuration
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Step 3: Base Table Configuration
08.49
| 00:00 | - Now that we've got the ECU ready to run the engine, we're going to look at configuring the base tables that we're going to need to be tuning. |
| 00:10 | And this is going to include the fuel base table, the ignition base table and we're also going to have a look at the lambda or your fuel ratio target table. |
| 00:20 | So let's start with our fuel base table. |
| 00:24 | So this is our three dimensional table of engine volumetric efficiency values, and we have on our vertical axis here, we have our engine speed, engine rpm, and on the horizontal axis we have our manifold pressure. |
| 00:40 | Note that in this instance, we're looking at gauge pressure, so zero kPa is atmospheric pressure, and as the inlet manifold vacuum increases, we move out to the left, into the negative values on this table. |
| 00:58 | In order to make changes to the axes, we can click on the table axes set-up icon here, and we can adjust them to suit. |
| 01:08 | So first of all we have our axes, which in this case is fuel load, so you'll remember that was configured already, in our main setup to be manifold pressure. |
| 01:20 | Now we've got the particular sites listed here, and what we can do is just adjust these sites as we require. |
| 01:30 | So in this case we've got a few more sites than I really think we need to get started, so we can simply click on the sites that we don't want, and remove them. |
| 01:41 | It's very easy. |
| 01:42 | Now what I'm going to do is start by having sites every 20 kPa, and remember it's still worthwhile to have some additional resolution in around the idle and cruise areas, so what I'm going to do is add a zone back in at minus 30 kPa, and let's add one in as well at minus 50 kPa. |
| 02:03 | So this is going to give us slightly finer resolution. |
| 02:06 | Of course we can always make changes to this at a later point if we wish. |
| 02:11 | Likewise, in our rpm axes, we're going to start by just removing a few sites so we're setting up something that is configured with zones every 500 rpm to start with, and then once we've got that set up, we can add in a few zones. |
| 02:30 | Now our rev limit for this engine is 6500 rpm, so generally we like to have a zone that goes just above that. |
| 02:37 | So our highest zone here is 7000. |
| 02:41 | Now I'm going to add a zone by clicking the insert row button and we'll add one in at 750 rpm, so that's close to our target idle speed. |
| 02:52 | We're also going to add another zone here, at 1250 rpm. |
| 02:56 | It's often nice to have a little bit of tighter resolution around the transition from idle to actually driving the car, and it makes it a little bit easier sometimes to get accurate control over the fuel in that area. |
| 03:10 | So that's our fuel table, our volumetric efficiency table configured, and we can click OK. |
| 03:17 | You can see that that shrunk that table significantly. |
| 03:21 | Next we can actually put some numbers in this table to start with. |
| 03:26 | And the advantage with a volumetric efficiency-based system is that it is accounting directly for the engine capacity and the fuel system flow. |
| 03:38 | And we find that most engines will idle somewhere around about perhaps 50% volumetric efficiency. |
| 03:46 | And if we start by entering that value throughout the entire table, that's going to probably at least get us an engine that's going to start up and run. |
| 03:57 | Might not be perfect, but we're going to be able to very quickly tune from there. |
| 04:01 | So that's our base fuel or VE table configured. |
| 04:04 | Let's move on now and have a look at our base table for our ignition angle. |
| 04:10 | Now this has exactly the same axes, and we're going to make some changes here as well. |
| 04:16 | First of all, if we look at our rpm axes, you can see that they're already set in 500 rpm increments so we don't really have anything to do there. |
| 04:25 | What I'm going to do is again just remove some sites from our ignition timing table, which we don't really need, and again we're going to add in a little bit of extra resolution around our cruise area, so we've got a minus 30 and a minus 50 kPa zone. |
| 04:45 | So that's our ignition and our base fuel table set and ready to go. |
| 04:51 | You can see we've got a value at the moment of 15 degrees added throughout this table, and this is a nice, safe ignition angle. |
| 04:59 | I know from experience that this isn't going to result in knock, and it's a safe starting point for most engines, unless of course we're talking about turbocharged engines where as we move on to boost pressure we may retard the timing a little further. |
| 05:14 | What I'm going to do is just highlight the top two columns of this table, down at low rpm, so this would be wide open throttle at low rpm, and I'll just retard the timing slightly further, just to ensure we don't hit any problems with knock. |
| 05:30 | So that's got us a base ignition table setup that we know is going to be safe. |
| 05:36 | Lastly, we need to go to our lambda target table. |
| 05:41 | And the lambda target table is essential, it's a very critical part of a VE based fuel model because we need to enter into this table our actual lambda target. |
| 05:52 | So the actual air-fuel ratio lambda values that we want the engine to be running, and then we're going to tune the VE table until we actually meet these particular lambda targets. |
| 06:05 | So let's click on our setup again, and we're just going to make some slight adjustments to the zoning on this table to align, if you like, with the zones that we've got in our other tables, and just make everything work the same. |
| 06:24 | It's always easier if we're working with tables that have similar zones. |
| 06:31 | Now, what I'm going to do with this particular table is, I'm actually going to add a couple more zones. |
| 06:38 | I'm going to again add some zones like we saw in the fuel and ignition table around idle, but I'm also going to add a further one out at 90 kPa, and this allows us to more accurately control the transition from our cruise mixtures, or our stoichiometric AFR aim lambda one out to what we want to be running at wide open throttle if we desire. |
| 07:05 | OK, so we've got that setup now, and we need to look at adding some numbers into this table that make sense, and you can see I've already configured this to a degree. |
| 07:15 | We have a target lambda 1.0 or stoichiometric lambda target in the cruise and idle areas of our table. |
| 07:25 | Out at the wide open throttle area you can see that we're targeting right about 0.88 lambda and what I'm going to do now is adjust at the higher rpm. |
| 07:39 | I'm just going to set the target lambda a little bit richer to 0.87, and this is just going to help control combustion temperature when we're at very high throttle openings and high load. |
| 07:54 | And you can see that at the high rpm low load areas, we're also targeting slightly richer. |
| 08:02 | This isn't an area that we're going to expect the engine to be running in, this is more the sort of area we're going to be transitioning through on a throttle lift or a gear change, and the additional fuel here will help control combustion temperature, help cool the engine. |
| 08:19 | So we don't need to be too concerned about these being our final lambda targets, we can adjust this table, of course, later. |
| 08:28 | But it is important before we get started tuning to make sure that the numbers in this table are realistic, because these will be the lambda targets that we will be aiming for. |
| 08:39 | OK, we've got our base tables configured, we've got some sensible numbers in those tables, we're ready to move on with our next step. |
